As for the silver halide photographic materials, particularly color photographic materials for picture-taking use, those having a high photographic speed, reduced fog and excellent keeping quality, as represented by ISO 400 photosensitive materials (e.g., Super-HG-400 manufactured by Fuji Photo Film Co., Ltd.), which can be compared favorably with ISO 100 photosensitive materials in image quality, have enjoyed an increasing demand in recent years.
One known method which can meet such a demand involves converting a photographically useful group into a precursor in which the photographically useful group is bonded to a timing group, and timely releasing the photographically useful group in the course of photographic processing. Such a method is disclosed, e.g., in U.S. Pat. Nos. 4,432,845 and 4,847,383.
In the method disclosed therein, however, one molecule of precursor releases one molecule of photographically useful group. Accordingly, incorporation of such a precursor in quantity into a film causes an increase in film thickness to result in a lowering of sharpness and a raise in cost of production.